Organosilicon compound with isothiocyanate substituent bonded through divalent bridge

ABSTRACT

A NEW CLASS OF ORGANOSILICON COMPOUNDS HAVING AN ISOTHIOCYANATE GROUP BONDED TO THE SILICON ATOM THROUGH AN ALKYLENE BRIDGE OF AT LEAST THREE CARBON ATOMS, OR AN ALKYLENE BRIDGE HAVING SULFUR OXYGEN OR NITROGEN LINKAGES THEREIN IS MADE BY REACTING THE CORRESPONDING AMINO ALKYL SUBSTITUTED ORGANOSILICON COMPOUND WITH CARBON DISULFIDE AND A DIALKYL CARBODIIMIDE. THE COMPOSITIONS ARE EXTREMELY USEFUL WHERE BASE CLEAVAGE OF THE SILICON ATOM FROM THE ISOTHIOCYANATE SUBSTITUTED GROUP IS A PROBLEM, SUCH AS GLASS SIZING WHERE THE GLASS IS BASIC AND THE FORMATION OF POLYURETHANES WHERE A BASE CATALYST IS IMPLIED.

United States Patent Otfice 3,790,613 Patented Feb. 5, 1974 Int. Cl.C07f 7/08, 7/18 US. Cl. 260-448.8 R Claims ABSTRACT OF THE DISCLOSURE Anew class of organosilicon compounds having an isothiocyanate groupbonded to the silicon atom through an alkylene bridge of at least threecarbon atoms, or an alkylene bridge having sulfur oxygen or nitrogenlinkages therein is made by reacting the corresponding aminoalkylsubstituted organosilicon compound with carbon disulfide and adialkyl carbodiimide. The compositions are extremely useful where basecleavage of the silicon atom from the isothiocyanate substituted groupis a problem, such as glass sizing where the glass is basic and theformation of polyurethanes where a base catalyst is implied.

BACKGROUND OF THE INVENTION Related applications This application is adivision of Ser. No. 151,549, filed June 9, 1971, and is acontinuation-in-part of the copending application of Abe Berger, Ser.No. 796,647, filed Jan. 31, 1969, now US. Pat. 3,646,089 and is relatedto the copending application of Abe Berger, Ser. No. 788,960, filed Jan.3, 1969, now 11.8. Pat. 3,642,855.

Prior art Organosilicon compounds having alkyl isocyanate substitucntsare known in the art and can be produced easily by the addition of achlorosilicon hydride across the olefinic double bond of an olefinicisocyanate, employing platinum catalysis. However, attempts to make thecorresponding alkyl isothiocyanates have been unsuccessful, possiblybecause of the poisoning eifect of the sulfur in the isothiocyanate onthe platinum catalyst. Organosilicon isothiocyanates have been preparedaccording to the method described in US. Pat. No. 3,l78,39lHoltschmidtet al., but, while the isothiocyanate group is bonded to a carbon atom,the thus substituted carbon group is bonded to the silicon atom throughan oxysilicon linkage. As is well known, such linkages are not as stableas the silicon-carbon linkage.

In addition, triorganosilylmethylisothiocyanates are made by thedecomposition of the dithiocarbamic acid as is shown in US. Pat. No.2,762,826-No1l. Again, when the isothiocyanate group is separated fromthe silicon atom by only one carbon atom such linkages are not as stableas when the isothiocyanate radical is separated by three or more carbonatoms. Stability against cleavage is of great importance in suchapplication as sizing glass fibers wherein the glass fiber surfacecontains alkali metal oxides rendering it extremely basic and in theformation of polyurethane foams where a basic catalyst is employed.

Similarly, While dithiocarbamyl-substituted organosilicon compounds havebeen prepared, where the dithiocarbamyl group is linked to the siliconatom through an alkylene bridge, this process has not proven adaptableto the formation of isothiocyanates. A process for forming thesedithiocarbamyl-substituted organosilicon compounds is shown in US. Pat.2,938,046Morehouse. Thus, the prior art has not produced stable,isothiocyanate-substi tuted organosilicon compounds where theisothiocyanate is substituted through a bridge which includes asiliconcarbon bond. These materials are extremely useful in theproduction of particularly advantageous polyurethanes.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed toorganosilicon materials having an isothiocyanate group connected to thesilicon atom through a bridge having a silicon-carbon bond and havingthe formula:

where R is selected from the class consisting of alkyl, aryl, aralkyl,alkaryl, cyanoalkyl, cyanoaryl, and dialkylamino groups; R is a divalentradical selected from the class consisting of alkylene, oxyalkylene,sulfalkylene, and iminoalkylene radicals, where each oxygen, sulfur, and--NH group is attached to two carbon atoms, and when R is an alkyleneradical there is at least a three carbon bridge between theisothiocyanate group and the silicon; R" is a monovalent radicalselected from the class consisting of alkyl, alkyleneoxyalkyl,alkylenesulfalkyl, alkyleneiminoalkyl, and hydrogen, where each oxygen,sulfur, and -NH- group is attached to two carbon atoms, the total numberof carbon atoms between R and R, combined, being from 0 to 20; Y is alower alkoxy group; and a is from 0 to 3.

These organosilicon materials are prepared by reacting an organosiliconcompound, substituted through a bridge, with a silicon-carbon bond withan amine group, with carbon disulfide and a dialkyl carbodiimideaccording to the reaction:

NOS

Where R is an organic group of not more than 18 carbon atoms selectedfrom the class consisting of alkyl, aryl, aralkyl, alkaryl, cyanoalkyl,cyanoaryl, and dialkylamine radicals; R' is selected from the classconsisting of alkylene having 3 to 15, oxyalkylene, thioalkylene, andiminoalkylene, where each oxygen, sulfur, or NH-- group is attached totwo carbon atoms; R" is selected from the class consisting of alkyl,alkyleneoxyalkyl, alkylenethioalkyl, and alkylcneazaalkyl and hydrogen,where each oxygen, sufur, and -NH group is attached 'to two carbonatoms, the total number of carbon atoms in R and R", combined, beingfrom 0 to 20; Y is a lower (C -C alkoxy group; R' is selected from theclass consisting of alkyl and cycloalkyl radicals of from 1 to 10 carbonatoms; and a is from 0 to 3.

The reaction is carried out in the presence of an ether solvent attemperatures of from 0 to 30 C. Reaction time is generally from 2 to 3hours after which the thiourea precipitates, indicating completion ofthe reaction. The product can then be recovered by a flash distillation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the presentinvention, an organosilicon compound having an amine substituentattached to the silicon atom through a bridge having a silicon-carbonbond is reacted with carbon disulfide and a dialkyl carbodiimide 3 inthe presence of an ether to yield an organosilicon compound having anisothiocyanate group, similarly bridged to the silicon compound througha bridge having a siliconcarbon bond according to the reaction ofequation:

Among the radicals which R represents are alkyl radicals such as methyl,ethyl, propyl, butyl, octyl, dodecyl, isopropyl, isobutyl, etc.;cycloalkyl radicals such as cyclophenyl, tolyl, xylyl, etc.; aralkylradicals such as benzyl, phenyl, biphenyl, naphthyl, benzoylphenyl,para-phenoxyphenyl, tolyl, xylyl, etc.; aralkyl radicals such asbenzy-l, phenethyl, etc.; cyano-substituted radicals such ascyanomethyl, alpha-cyanoethyl, beta-cyanoethyl, beta-cyanopropyl,gamma-cyanopropyl, cyanophenyl, etc.; and dialkyl amine radicals such asdimethyl amine. The preferred substituents represented by R aremonovalent alkyl radicals of from 1 to 7 carbon atoms.

R represents alkylene radicals such as ethylene, propylene, dodecylene,etc.; and alkylene chains with a hetero atom linkage, such as:

The radicals represented by R" are monovalent and similar to thoserepresented by R and include such alkyl substituents as methyl, ethyl,propyl, butyl, isopropyl, isobutyl, etc.; and monovalent radicals havinga hetero atom linkage, such as:

The alkyl and cycloalkyl radicals represented by R include methyl,ethyl, propyl, decyl, cyclopentyl, cyclohexyl, etc. Y is a lower alkoxygroup and includes methoxy, ethoxy, isopropoxy, etc.

The reaction between the organosilicon atom with the amine group linkedthrough a bridge having a siliconcarbon bond, the carbon disulfide, andthe dialkyl carbodiimide is carried out in the presence of an ethersolvent. The three reactants are generally present in stoichiometricamounts, though there can be a 10% excess, based upon the stoichiometricrequirements of either. The carbon disulfide'can be present in an excessof as much as 30 mole percent, based upon the stoichiometric.

The solvents employed in the reaction are ethers, including both alkyland cyclic ethers. Preferably, the reaction is carried out intetrahydrofuran, though ethyl ether and other ethers can also beemployed. The total of the three reactants generally comprises fromabout 20 to 60% by weight of the ether solvent employed. Initially, eachof the reactants is soluble in the ether solvent, but followingreaction, the thiourea precipitates from the solvent.

The reaction is generally carried out at a temperature of from to 30 C.and the order of addition of the reactants to the reaction mixture isimmaterial. The time of reaction is generally from about 2 to 3 hoursand then, as previously noted, the thiourea precipitates from thesolution. This is an indication that the reaction is complete. Thesolids are then filtered from the reaction mixture, the solvent,stripped, and the reaction mixture fractionated. Additionally, a flashdistillation can be employed to purify the organosilicon compound nowhaving the isothiocyanate group linked through a bridge having asilicon-carbon bond.

The products which can 'be formed according to the present inventioninclude the following:

(CHs)a(CHaO) Si(CHs)aNCS (C H5) (CHsO) gSi (CH1) 2 C H-CH;

N C S (CuHu) 3) z l z) 3- 2 C N C S (CHsCN) (C 2H5) gsi (CH2) 3NE (CH2)tNCS 21150); Si. (CH3) 3-S-'CH2-'NC S This list should, of course, notbe considered exhaustive of the possible compounds to be formedaccording to the present invention.

The formation of the materials of the present invention, according tothe process of the invention, will now be described in greater detail inthe following examples. These examples should be considered asillustrative only, and not as limiting in anyway the full scope of theinvention as covered in the appended claims. All parts in the followingexamples are by weight.

EXAMPLE 1 Into a reaction vessel were placed parts of drytetrahydrofuran, 21.1 parts N,N-dicyclohexylcarbodiimide and 12.5 partsof carbon disulfide. The reaction mixture was cooled to 10 C. employingan external refrigerant. After the reaction mixture had reached thedesired temperature, a quantity of 14.7 parts ofaminopropyldimethylmethoxysilane was added, dropwise, and a mildexotherm was noted. When about one-half of this organosilane had beenadded, the reaction mixture became cloudy and a precipitate ofdicyclohexylthiourea began to precipitate. After completion of theorganosilane addition, the reaction mixture was warmed to roomtemperature and the dicyclohexylthiourea which had formed was removed byfiltration. The tetrahydrofuran and ex cess carbon disulfide wereremoved by an atmospheric distillation and the remaining reactionproduct was then fractionated. The desired product distilled at 81 C.and 0.5 mm. pressure and a vapor phase chromatography scan indicated apurity of approximately 98%. An infrared scan, with absorption at 4.52.and 4.7 microns, characteristic of -NCS absorption, was consistent withthe structure:

EXAMPLE 2 A quantity of 21.1 parts N,N-dicyclohexylcarbodiimide, 12.5parts carbon disulfide, and 90 parts of dry tetrahydrofuran was placedinto a reaction vessel and the mixture was cooled to 10 C. employing anexternal refrigerant. A quantity of 23.7 parts ofaminopropoxypropyltrimethoxysilane was then added to the reactionmixture, dropwise, and a mild exotherm was noted. The temperature of thereaction mixture was maintained at 10 C. i5 C. by controlling the rateof addition of the organosilane. After the addition was completed, thereaction mixture was allowed to warm to room temperature and after aboutone-half hour, the mixture became cloudy and a precipitate ofdicyclohexylthiourea appeared. The reaction mixture was allowed toremain in the vessel for an additional 3 hours after which thedicyclohexylthiourea was separated by filtration and the tetrahydrofuranremoved by atmospheric distillation. The remaining reaction mixture wasthen fractionated and the product was collected at 125-126 C. at 0.3 mm.as a colorless oil. A vapor phase chromatography scan showed a purity ofapproximately 99% and the infrared scan was consistent with thestructure:

(CH O Si (CH O (CH NCS EXAMPLE 3 When theaminopropoxypropyltrimethoxysilane employed in Example 2 is replacedwith a corresponding amount of s s) 2 5 a 2) z 2) 2 2 the product:

(CGH5) 2 5 z 2 z 2) z results.

EXAMPLE 4 When the aminopropoxypropyltrimethoxysilane of Example 2 isreplaced with an equivalent quantity of:

(( 1) :N) |)2 H2) 2-SC Hz- H Ha the product:

((CHOrN)(CH;) Si(CH2)z-S-CH;CHCH;

NC s

results.

EXAMPLE 5 When the aminopropyldimethoxysilane of Example 1 is replacedwith an equivalent quantity of:

( ZHB)I 2)I 7 the product:

(OiHQSKCHzh-CH-C1H NCS results.

The products produced according to the process of the present inventionare valuable starting materials in the preparation of polythiourethanesthrough isothiocyanate additions. The plastics which are thus producedcan be either porous or non-porous and, according to their form, can beused as gears, diaphragms, and as cushioning materials.

What I claim is:

1. Organosilicon materials having an isothiocyanato group connected tothe silicon atom through a bridge having a silicon-carbon bond andhaving the formula:

where R is an alkyl radical; R is a divalent radical selected from theclass consisting of alkylene, sulfalkylene, and divalentnitrogenalkylene radicals, where each oxygen, sulfur, and NH group isattached to two carbon atoms, and when R is an alkylene radical there isat least a three carbon bridge between the isothiocyanato group and thesilicon; R" is a monovalent radical selected from the class consistingof alkyl, alkyleneoxyalkyl, alkylenethioalkyl, alkylenenitrogenalkyl,where each oxygen, sulfur, and NH- group is attached to two carbonatoms, the total number of carbon atoms between R and R, combined, beingfrom 0 to 20; Y is a lower alkoxy group and a is from 0 to 3.

2. The organosilicon compound of claim 1 wherein R is a sulfalkylenegroup.

3. The organosilicon compound of claim 1 wherein R' is a divalentnitrogen-alkylene group.

4. The organosilicon compound of claim 1 wherein R is an alkylene grouphaving at least 2 carbon atoms.

5. The organosilicon compound:

(CH (CH O)Si(CH NCS References Cited UNITED STATES PATENTS 2,762,8269/1956 Noll 260448.2 N

3,466,314 9/1969 Moedritzer et al. 260448.2 N

3,646,089 2/ 1972 Berger 260448.2 N X DANIEL E. WYMAN, Primary ExaminerP. F. SHAVER, Assistant Examiner U.,S. Cl. X.R.

